I was recently asked how pre-K’s effects compared with the usual income gaps in kindergarten readiness. How much can high-quality pre-K do to help children from low-income families catch up to children from more middle-class families?
My paper with Gormley and Adelstein on Tulsa pre-K provides an answer to this question. In this paper, the average test score gap at kindergarten entrance between children eligible for a free lunch, and children who must pay full price, is 14 percentile points.
Half-day pre-K for one school year raises test scores of low-income children about 12 percentile points. Full-day pre-K for one year raises test scores of low-income children about 18 percentile points.
Therefore, research suggests that even one-half day of pre-K for only one school year will close most of the gap across income groups in kindergarten readiness. A full-day of pre-K more than closes these income gaps.
Of course, if pre-K is universal, these income gap-closing features are reduced. Universal pre-K helps children from all income groups, but has stronger percentage effects for children from low-income families. But universal pre-K will help raise the overall achievement levels, productivity, and economic future of the entire economy, which is a goal worth pursuing. Universal pre-K increases the size of the overall economic pie, while helping low-income groups the most in percentage terms. Universal pre-K advances both economic efficiency and equity goals.